Unsymmetrical diphenolic compounds

ABSTRACT

4-[[4-hydroxy-3,5-bis(1-methylethyl)phenyl]hydrocarbyl]-2, 6-dimethylphenols. 
     The compounds of the invention such as 4-[[4-hydroxy-3,5-bis(1-methylethyl)phenyl]hydrocarbyl]-2,6-dimethylphenol have low melting points and other physical and chemical properties making them valuable as curing agents, antioxidants, and for other purposes.

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention relates in general to new aromatic diphenolic (diol)compounds which have various utilities and desirable physical andchemical properties.

II. Description of the Prior Art

Various bisphenols and similar compounds have been made according toprocesses of the prior art but there exists a need for aromaticdiphenolic compounds having desirable properties for a variety of uses.

CROSS-REFERENCE

Reference is made to co-pending application Ser. No. 598,225, filed Apr.9, 1984, in the name of Kju Hi Shin. Said application and thisapplication are commonly assigned.

SUMMARY OF THE INVENTION

The present invention is directed to providing compounds having goodphysical properties for various utilities, said compounds being of aparticular unsymmetrical structure which has been found to impartdesirable physical and chemical properties. The present inventioncomprises compounds of structure I: ##STR1## wherein R is H or a radicalselected from the group consisting of alkyls, alkenyls, cycloaliphatics,aromatics, heteroatomics, and heterocyclics. The alkyls and alkenyls arepreferably 1-7 carbon atoms. The cycloaliphatics are preferably 3-7carbon atoms. The aromatics are preferably 6-10 carbon atoms. Theheterocyclics are preferably 5-7 member rings. The heteroatomicspreferably contain 1-7 atoms other than hydrogen usually carbon andoxygen.

The compounds of the present invention are usable as diol chainextenders for reaction with organic polyols and organic polyisocyanatesto form polyurethanes having a broad scope of application. The compoundsof the present invention are also usable as antioxidants to protectorganic materials including hydrocarbon lubricating oils andpolyolefins. The compounds of the present invention are also usable ascuring agents for epoxies and the like or as intermediates for synthesisof a variety of end products. The most preferred compound of the presentinvention is4-[[4-hydroxy-3,5-bis(1-methylethyl)phenyl]methyl]-2,6-dimethylphenolwhich may also be denominated [3,5-diisopropyl-4-hydroxyphenyl][3',5'-dimethyl-4'-hydroxyphenyl] methane,4-[[4-hydroxy3,5-diisopropylphenyl]methyl]-2,6-dimethylphenol,2,6-diisopropyl4-(3,5-dimethyl-4-hydroxybenzyl)phenol or4-(2,6-diisopropyl-4-hydroxybenzyl)-2,6-xylenol. ##STR2## This compoundis preferred because it has a low melting point and other desirablephysical and chemical properties for chain extender, antioxidant, andother uses.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides compounds of structure I: ##STR3##wherein R is H, alkyl, alkenyl, cycloaliphatic, aromatic, heteroatomic,or heterocyclic.

The compounds of the present invention have two phenolic moieties withmethyl substituents in the two positions ortho to the hydroxyl group ofone phenolic moiety and isopropyl substituents in the two positionsortho to the hydroxyl group of the other phenolic moiety. These phenolicmoieties are bridged by a divalent group to form the compounds of theinvention which because of the unsymmetrical positioning of theisopropyl and methyl substituents relative to the two phenolic moietiesand the symmetrical positioning of the isopropyl and methyl substituentson the individual phenolic moieties have good physical and chemicalproperties for both reactivity and stability in their intended uses.

The compounds of the invention may be synthesized by two methods. Thepreferred methylene-bridged compound of the invention may be preparedfrom (2,6-diisopropyl-4-hydroxybenzyl) (hydrocarbyl) ethers by reactingsuch an ether with 2,6-dimethylphenol in the presence of a strong acidsuch as H₂ SO₄ at about 0°-10° C., preferably 0°-5° C. The precursorethers may be obtained by the process of Filbey, U.S. Patent No.2,838,571 which is incorporated herein by reference.

The compounds of the invention generally may be obtained by a processdisclosed in commonly assigned copending application Ser. No. 598,225,filed Apr. 9, 1984 According to that process 2,6-dimethylphenol or2,6-diisopropylphenol is added (preferably gradually) to a refluxingsolvent portion of an alcohol with a secondary amine and an aldehyde.The aldehyde is of the type RCHO wherein R is as set forth above.

The divalent radical ##STR4## attaches at the para position of thephenol and an ether of structure II is formed: ##STR5## where the R' areeither both methyl or both isopropyl, the R" is a hydrocarbyl group(preferably alkyl) provided from the alcohol and R is as set forth abovefor the bridging group. The ether is then reacted with2,6-diisopropylphenol or 2,6-dimethylphenol as required to make a novelcompound of the invention. Thus the choice of aldehyde used to make theprecursor ether determines the divalent bridging group of the compoundsof the invention.

Most aldehydes are suitable for use according to the invention but thosewith twelve or fewer carbon atoms are more readily used to make theethers of structure II. Those with eight or fewer carbon atoms are morepreferred. The aldehydes usable with the invention include formaldehyde,acetaldehyde, butyraldehyde, benzaldehyde, benzylaldehyde,propionaldehyde, benzalacetaldehyde (cinnamaldehyde--(C₆ H₅)CH═CH--CHO),cuminicaldehyde ((CH₃)₂ CH (C₆ H₄)CHO or para-isopropylbenzaldehyde),heptylic aldehyde, furfuraldehyde, crotonaldehyde, and glyoxalic acidand its esters.

The phenolic groups of the compounds of the invention are bonded to thesame carbon atom which is part of the divalent radical bridge. That isthe divalent radical from the aldehyde always bridges the phenolicmoieties across a single carbon atom.

Accordingly, the divalent radicals which bridge the phenolic moietiesinclude furfurylidene, propenylidene, benzylidene, β-phenethylidene##STR6## methylene, ethylidene, propylidene, butylidene,isobutyrilidene, cyclohexylmethylene, 2,2-dimethylpropylidene,propenylidene ##STR7## and the divalent radicals from glyoxalic acid andits esters such as ##STR8## wherein the R" is a hydrocarbyl radical. Theradical ##STR9## may be obtained by hydrogenation of benzaldehyde priorto use in the production of the ethers of structure II.

From the above it is clear that the R of structures I and II may, amongother radicals, be alkyls such as methyl, ethyl, propyl, isopropyl,n-butyl, isobutyl, sec-butyl, n-hexyl, and the like; cycloaliphaticssuch as cyclohexyl or cyclopentyl; aromatics such as phenyl, benzyl orcumyl; heterocyclics such as the monovalent furan radical fromfufurylidene; heteroatomics such as the radicals ##STR10## fromglyoxalic acid and its esters; and alkenyls such as ethenyl, propenyl,and the like.

It can be seen that the compounds of the invention have the phenolicmoieties bonded to the same carbon atom.

According to the invention, stablized organic compositions are providedwhich contain a compound of structure I of the invention.

The compounds of the invention can be used as antioxidants in a broadrange of organic material normally subject to gradual degradation in thepresence of oxygen during use over an extended period. In other words,the organic compositions protected by the present antioxidants are thetype in which the art recognizes the need for antioxidant protection andto which an antioxidant of some type is customarily added to obtain anextended service life. The oxidative degradation protected against isthe slow gradual deterioration of the organic composition rather than,for example, combustion. In other words, the present additives are notflame retarding additives nor flame suppressing additives and thedegradation protected against is not combustion but, rather, the gradualdeterioration of the organic composition due to the effects of oxygenover an extended period of time.

Examples of organic materials in which the additives are useful includepolymers, both homopolymers and copolymers, of olefinically unsaturatedmonomers, for example, polyolefins such as polyethylene, polypropylene,polybutadiene, and the like. Also, poly-halohydrocarbons such aspolyvinyl chloride, polychloroprene, polyvinylidene chloride, polyfluoroolefins, and the like, are afforded stabilization. The additives provideantioxidant protection in natural and synthetic rubbers such ascopolymers of olefinically unsaturated monomers includingstyrene-butadiene rubber (SBR rubber), ethylene-propylene copolymers,ethylene -propylenediene terpolymers such as the terpolymer of ethylene,propylene and cyclopentadiene or 1,4-cyclooctadiene. Polybutadienerubbers such as cis-polybutadiene rubber are protected.Poly-2-chloro-1,3-butadiene (neoprene) and poly-2-methyl-1,3-butadiene(isoprene rubber) are stabilized by the present additives. Likewiseacrylonitrile-butadiene-styrene (ABS) resins are effectively stabilized.Ethylenevinyl acetate copolymers are protected, as arebutene-methylacrylate copolymers. Nitrogen-containing polymers such aspolyurethanes, nitrile rubber, and lauryl acrylate-vinyl -pyrrolidonecopolymers are effectively stabilized. Adhesive compositions such assolutions of polychloroprene (neoprene) in toluene are protected.

Petroleum oils such as solvent-refined, midcontinent lubricating oil andGulf Coast lubricating oils are effectively stabilized. In hydrocarbonlubricating oils, both mineral and synthetic, the present additives maybe used in combination with a zinc dihydrocarbyldithiophosphate, e.g.zinc dialkyldithiophosphate or zinc dialkaryldithiophosphate.

The antioxidants of the present invention may be used with mineral oilswhether obtained by solvent refining, hydrotreating, hydrocracking, oranother method. Thus the antioxidants of the present invention aresuitable for combination with a mineral oil of lubricating viscositywhich is derived from a lubricating oil produced by contacting ahydrocarbon feedstock with hydrogen preferably in the presence ofcatalyst effective to promote hydrocracking, at hydrocarbonhydrocracking conditions to produce an oil of lubricating viscosityhaving an increased viscosity index relative to the viscosity index ofthe hydrocarbon feedstock.

Typical applications of the antioxidant additives of this invention inoils include use in all motor oils, crankcase oil, turbine oil, dieseloil, industrial oil, hydraulic fluids and the like.

The antioxidant additives of the invention are also useful in fuelsincluding, but not limited to gasoline, alcohol, and the like.

Synthetic ester lubricants such as those used in turbines and turbojetengines may be stabilized. Typical synthetic ester lubricants includedi-2-ethylhexyl sebacate, trimethylolpropane tripelargonate, C₅₋₉aliphatic monocarboxylic esters of pentaerythritol, complex estersformed by condensing under esterifying conditions, mixtures of polyols,polycarboxylic acids, and aliphatic monocarboxylic acids and/ormonohydric alkanols. An example of these complex esters is thecondensation product formed from adipic acid, ethyleneglycol and amixture of C₅₋₉ aliphatic monocarboxylic acids. Plasticizers such asdioctyl phthalate are effectively protected. Heavy petroleum fractionssuch as tar and asphalt can also be protected should the need arise.

Polyamides such as adipic acid-1,6-diaminohexane condensates andpoly-6-aminohexanoic acid (nylon) may be stabilized. Polyalkylene oxidessuch as copolymers of phenol with ethylene oxide or propylene oxide maybe stabilized. Polyphenyl ethers such as poly-2,6-dimethylphenyl etherformed by polymerization of 2,6-dimethylphenol using a copper-pyridinecatalyst may be stabilized. Polycarbonate plastics and otherpolyformaldehydes may also be protected.

Linear polyesters such as phthalic anhydride-glycol condensates may begiven a high degree of protection. Other polyesters such as trimelliticacid-glycerol condensates may also be protected. Polyacrylates such aspolymethylacrylate and polymethylmethacrylate may be stabilized.Polyacrylonitriles and copolymers of acrylonitriles with otherolefinically unsaturated monomers such as methylmethacrylates may alsobe effectively stabilized.

The additives can be used to protect any of the many organic substratesto which an antioxidant is normally added. It can be used whereeconomics permit to protect such substrates as asphalt, paper,fluorocarbons such as teflon, polyvinyl acetate, polyvinylidenechloride, coumarone-indene resins, polyvinyl ethers, polyvinylidenebromide, polyvinyl bromide, acrylonitrile, vinyl bromide copolymer,vinyl butyral resins, silicones such as dimethylsilicone lubricants,phosphate lubricants such as tricresylphosphate, and the like.

The additives are incorporated into the organic substrate in a small buteffective amount so as to provide the required antioxidant protection. Auseful range is from about 0.005 to about 10 weight percent, and apreferred range is from about 0.05 to 5 weight percent.

Methods of incorporating the additive into the substrate are well known.For example, if the substrate is liquid the additive can be merely mixedinto the substrate. Frequently the organic substrate is in solution andthe additive is added to the solution and the solvent removed. Solidorganic substrates can be merely sprayed with the additive or with asolution of the additive in a volatile solvent. For example, stabilizedgrain products result from spraying the grain with a toluene solution ofthe additive. In the case of rubbery polymers the additive can be addedfollowing the polymerization stage by mixing it with the final emulsionor solution polymerization mixture and then coagulating or removingsolvent to recover the stabilized polymer. It can also be added at thecompounding stage by merely mixing the additive with the rubbery polymerin commercial mixing equipment such as a Banbury blender. In thismanner, rubbery polymers such as styrene-butadiene rubber,cispolybutadiene or isoprene polymers are blended with the antioxidanttogether with the other ingredients normally added such as carbon clack,oil, sulfur, zinc oxide, stearic acid, vulcanization accelerators, andthe like. Following mastication, the resultant mixture is fabricated andmolded into a finished form and vulcanized.

The compounds of structure I of the invention are also usable in thepolyurethane arts, in particular for the preparation of polyurethanes byany of various methods including reaction injection molding (RIM),casting of elastomers, and spraying of elastomeric polyurethanecoatings. According to the invention, various organic polyisocyanatesare usable to form polyurethanes with the compounds of structure I ofthe invention. These include the 4,4'-methylenebis(phenylisocyanate)(MDI) which is a preferred diisocyanate for preparing RIM polyurethanes.The invention also includes polyurethanes derived from the compounds ofstructure I with other polyisocyanates such as the following substancesand mixtures thereof:

m-phenylenediisocyanates;

2,4-tolunediisocyanates;

2,6-toluenediisocyanates;

naphthalene-1,5-diisocyanates;

1,3,5-benzene-triisocyanates; and

polyarylpolyalkylenepolyisocyanates such as a

polymethylenepolyphenolisocyanate.

Isocyanates prepared by phosgenation of the reaction product betweenaniline and formaldehyde having a functionality of about 2.2 to about3.5 are known to those skilled in the art.

Polyurethanes of the invention are preferably made from the diols ofstructure I along with organic polyols. Among the organic polyols arethe diols which include, more preferably, the polyether diolspredominantly having 2 hydroxy groups bonded to primary carbon atoms.Typically in such more preferred materials up to about 90% of hydroxygroups present are primary. Polyether polyols suitable for use in thisinvention are made by polymerization of cyclic ethers such as ethyleneoxide, propylene oxide, butylene oxide, tetrahydrofuran, and the like.These cyclic ethers can be used individually or as mixtures or insuccessive fashion when making a polyether.

The organic compounds usable as polyhydroxy reactants for polyurethanesare the dihydroxy polyalkalene polyethers having at least 2 primaryhydroxyl groups and a molecular weight of from about 400 to about12,000, more preferably from about 400 to about 7,000.

Various catalysts including tin catalysts such as dibutyl tin dilaurateare usable according to the invention. U.S. Pat. No. 4,218,543 disclosesa variety of catalysts for the RIM process and that patent isincorporated herein by reaerence in its entirety.

Polyurethanes produced by the above described reactants are extended,i.e., chain-lengthened by the compounds of structure I of the inventionwhich react with the isocyanates used in the polyurethane arts.Furthermore, the compounds of the invention are substantially free ofgroups which react with the isocyanates to terminate a polyurethanechain formation.

The compounds of structure I of the invention are low melting solids atroom temperature and are soluble/dispersable in the polyols used in theRIM or other polyurethane processes.

For cast elastomer processes using the compounds of structure I of theinvention the polyols are usually of a molecular weight of about1,000-3,000 and may be of the polyester or polyether type reacted with astoichiometric excess of diisocyanate to produce a prepolymer. Chainextension is then carried out with the chain extender compound of thestructure I compounds of the invention.

Suitable polyester polyols that can be used may be based on polyesterglycols such as poly(ethylene adipate), poly(ethylene/propyleneadipate), poly(ethylene glutarate), and poly(ethylene pimelate).

Various other components may be added to a polyurethane system using thecompounds of structure I of the invention. These include a flameretardant, emulsifiers, foam stabilizers, reaction decelerators such asHCl, dyes, fillers, and the like.

The compounds of structure I of the invention may be made according tothe processes of the following non-limiting examples.

EXAMPLE 1

This example demonstrates a method of preparation of one of a variety ofprecursor ethers of the invention.

Methanol, 440 ml., 48 grams paraformaldehyde, and 6 grams of a 40percent aqueous solution of dimethylamine are charged to a three-neckround bottom flask and refluxed (about 65° C). A solution of2,6-diisopropylphenol (178.28 grams--1 mole) in 100 ml. methanol isadded dropwise over a period of more than two days. Seven gaschromatography (GC) analyses were taken at representative intervals.They indicated a slow but progressing reaction. After the first GC (onehour) 2.91 grams (0.024 mole) N-methyltoluidine were added. After thefourth GC (21 hours), 5.95 grams (0.05 mole) N-methyltoluidine, 24.87grams (0.829 mole) paraformaldehyde, and 100 ml. methanol were addedwhile the reaction continued. After 27 hours, 75 ml. methanol and 10.6grams 40% dimethylamine were distilled off and the refluxing was thencontinued. At 45 hours, the seventh GC indicated 1.0 area percent2,6-diisopropylphenol, 35.5 area percent 2,6-diisopropyl-α-methoxy-p-cresol; 5.3 area percent 2,6-diisopropyl-α,α-dimethoxy-p-cresol; anda small amount of 4,4'-bis(2,6-diisopropylphenol). The reaction productwas slightly yellow-brownish in color. The solution was concentrated andthe precipitated crystals were filtered and recrystallized fromisooctane, given two methanol washings, and dried in vacuum. A GCanalysis indicated 95 percent of the desired2,6-diisopropyl-α-methoxy-p-cresol product which was dried in vacuum atroom temperature. The yield was 57.4 grams having a melting point of85.5-86.0. The solvent taken off still contained a large amount ofproduct (very soluble in methanol) some of which precipitated. Theresidue after distilling off the solvent was crystallized from an oilydark red liquid and filtered off. After washing and recrystallization,another 85.6 grams product were obtained for a total yield of 143 grams(64.4 percent). The structure was confirmed by NMR and GC/massspectroscopy.

EXAMPLE 2

The following example is a method of preparation of the compounds of thepresent invention from the precursor ether of Example 1.

Portionwise over a period of about two hours and 15 minutes, 122.54grams (0.552 mole) of 2,6-diisopropyl-α-methoxy-p-cresol (an ether) wasadded to a mixture of 101.29 grams (0.829 mole) 2,6-dimethylphenol and114.6 grams of 78 percent sulfuric acid in 690 ml. of methylenechloride. The reaction was carried out at atmospheric pressure and 4°-6°C. under a nitrogen atmosphere with mechanical stirring in a two literthree-neck flask. The temperature was maintained with an ice water bath.Immediately after the eighth of thirteen ether portions had been added,no ether could be detected by gas chromatography analysis (GC),indicating a very fast reaction. After the total addition of the ether,the reaction mixture was allowed to come to room temperature and asecond GC indicated no ether present; 90.74 area percent of productphenol, 4-[[4-hydroxy-3,5-bis(1-methylethyl)phenyl]methyl]-2,6-dimethyl; and some dimethylphenol. The mixture wasslightly pinkish to yellow-orange. The mixture was transferred to aseparatory funnel and rinsed out of the flask with methylene chloride.The heavy sulfuric acid layer was drained off. Water was added and themixture agitated. Additional methylene chloride was added followed bytwo 150 ml. water washes.

The methylene chloride and excess 2,6-dimethylphenol was distilled offunder vacuum. The viscous liquid product was crystallized in 276 ml.isooctane using seed crystals from a previous run. The product wasfiltered and rinsed with 50 ml. cold isooctane. The product meltingpoint was only 73°-75° C. and the yield was about 160 grams (about 93percent).

The various aspects and permutations of the invention may be variedwithout departing from the scope or spirit of the invention as definedby the following claims.

We claim:
 1. A compound of structure I: ##STR11## wherein R is H, alkylor alkenyl of 1 to 7 carbon atoms, cycloaliphatic of 3 to 7 carbonatoms, aromatic of 6 to 10 carbon atoms, a 5 to 7 member heterocyclicring, or a heteroatomic radical of 1 to 7 atoms other than H.
 2. Acompound of claim 1 wherein R is an alkyl of 1 to 7 carbon atoms.
 3. Acompound of claim 1 wherein R is phenyl.
 4. The compound4-[[4-hydroxy-3,5-bis (1-methylethyl)phyenyl]methyl]-2,6-dimethylphenol: ##STR12##